This invention relates to a signal transmitting apparatus using orthogonal frequency division multiplexing. This invention also relates to a signal receiving apparatus using orthogonal frequency division multiplexing.
Orthogonal frequency division multiplexing (OFDM) uses multiple carriers which are modulated in accordance with information to be transmitted. The carriers have an orthogonal relationship with each other. Data transmission based on OFDM is executed symbol by symbol. Each OFDM transmission symbol interval is composed of a guard interval and an effective symbol interval. The guard interval is used for reducing multipath effects. The effective symbol interval is used for transmitting data.
In an OFDM receiver side, the reproduction of carriers without time-base variations in phases is generally required to accurately recover transmitted data. Various factors hinder such good reproduction.